1) Field of the Invention
The present invention relates to a technology for slowing down speed of a vehicle in response to a relation of the vehicle with an object.
2) Description of the Related Art
Now-a-days some of the cars are provided with a vehicle deceleration control apparatus. The vehicle deceleration control apparatus detects another vehicle running in front of the vehicle, and automatically slows-down the speed of the vehicle if a distance between the vehicle and the another vehicle is less than a specific distance that allows safe driving. The vehicle deceleration control apparatus detects the other vehicle and distance between the vehicle and the other vehicle using, for example, radar waves. The control of lowering the speed of the vehicle will be called as deceleration control.
Some vehicle deceleration control apparatuses stop the deceleration control while the driver is accelerating the vehicle, by pressing the accelerator pedal (accelerator override) or so, and start the deceleration control again once the accelerator override has been terminated. However, if the deceleration controller is performed immediately after the termination of the accelerator override, the driver feels uncomfortable due to a phenomenon called a deceleration shock.
As a countermeasure, Japanese Patent Application Laid Open (JP-A) No. 2001-18680 discloses to insert a time gap between a timing at which the accelerator override ends and a timing at which the deceleration controller is to be started again. In other words, it is assumed that the driver is intentionally approaching the other vehicle, and the driver has intentionally slowed-down the vehicle; so that, the deceleration controller is not performed.
JP-A No. 2000-355233 discloses another conventional technology. Assume that a vehicle is following (chasing) another vehicle, the vehicle temporarily stops following the other vehicle and restarts following the other vehicle. The technology disclosed in JP-A No. 2000-355233 teaches to limit lowering the speed of the vehicle to a specific speed while the vehicle has temporarily stopped following the other vehicle. This arrangement reduces the unpleasant deceleration shock.
JP-A No. 2001-18680 and JP-A No. 2000-355233 each discloses a technique to reduce the unpleasant deceleration shock; however, the driver can feel uncomfortable even immediately after the driver lowers the speed of the vehicle. This is explained in detail below.
Drivers often intentionally slow-down vehicle by applying brakes, or the vehicle usually slow-down while the gears are being shifted. If the deceleration control is applied immediately after the vehicle has slowed-down, the vehicle is slowed-down further so that the driver feels that the vehicle has slowed-down in excess than what he has anticipated. This make the drivers uncomfortable.